STRUCTURAL LOCUS OF TRANSMUCOSAL ALBUMIN EFFLUX IN CANINE ILEUM - FLUORESCENT STUDY

Abstract

The effects of elevated intestinal venous perssure on the intestinal tissue spaces and the histological locus of the transmucosal albumin flux under such conditions were demonstrated in 10 mongrel dogs. Albumin was localized in the tissues using an Evans blue-albumin fluorescence technique. This technique makes use of the fluorescence properties and albumin affinity of Evans blue dye (T-1824). Evans blue dye has a high affinity for albumin and emits a red-orange fluorescence at a wavelength of 720 nm. Evans blue was mixed with a solution of bovine serum albumin at concentrations that yield negligible amounts of free dye. Control ileal samples were obtained in order to visualize the natural tissue morphology and fluorescence. The Evans blue-albumin solution was injected and tissue samples were obtained 15 and 60 min postinjection, then venous outflow was occluded and after 15 and 60 min the tissues were sampled. Each sample was immediately frozen, freeze dried, embedded in paraffin and 7.mu. sections were made. The Evans blue-albumin was demonstrated histologically with a fluorescence microscope. No leakage sites were apparent at normal venous pressures. After elevation of venous pressure, Evans blue-albumin was observed in the interepithelial and/or intraepithelial spaces of villus tips, but no Evans blue-albumin was observed either between or within the epithelial cells of the crypts, or within the tubular crypt lumina. At elevated venous pressures, the transmucosal albumin flux occurred exclusively at the villus tip region, suggesting a great vulnerability of the cells found in this region to elevations in tissue pressure as compared to the crypt epithelial cells.